Sophisticated communications use systems that are directed towards the blind and adaptive establishment of thresholds for signal detection. More specifically the thresholds are derived “blindly”. As is typical of blind signal processing the receiving system only has access to the channel outputs, and no knowledge or information regarding the environment being sensed. Blind processing has well known advantages, in particular when the transmission system may be non-cooperative or autonomous with respect to the reception system. The advantages also present challenges.
For example one key challenge for a signal detection system operating blindly is to set a signal detection threshold. Normally this is performed using a sequence of known noise-only samples to estimate noise power and hence derive a threshold suitable to meet a desired probability of false alarm (Pfa). In many blind systems, no such labeling of the received data is possible. Hence the signal detection system is operative to set a threshold in the presence of signal components. There are many uses for such a threshold, and those skilled in the art will recognize the value of such a system capability.
The system disclosed herein is operative to adaptively set signal detection thresholds to meet a Pfa requirement. Adaptation is achieved by repeating the noise estimation processing on some scheduled interval. In each interval, for each channel, the noise estimates are generated from correlation matrices developed using data sampled from the receive channel(s). The adaptation feature is particularly useful when the environment may have non-stationary noise and changing co-channel signal environment.
In addition, the system has the novel capability to indicate a quality metric which indicates the potential level of bias or contamination in the noise estimates by signal components. Based on the quality metric the noise estimate can be rejected as “unusable” depending on the needs of a particular application.